I have a 89 IROC L98 with the dual fan setup. When I first got the car I was poking around under the hood and noticed that one of the fans wiring was cut and taped up. I thought maybe the fan was bad and pulling to many amps and causing problems. Just out of curiosity I wired it back up. Started the car and let it idle. It got as hot as I felt comfortable and neither fan had come on. So I started reading and found I could ground the Green/White wire from each relay and make the fans come on. They both worked fine only when I disconnected the ground the fans stayed on until I shut the car off. So, now I've read some more and found that one fan is controlled by the ECM and it's turn on temp is 226* I think it said. The second fan is controlled by a switch mounted in the engine or head and is set for around 238* or so.

In summary, there may be no problems with my fans except I don't feel comfortable letting the car run hot enough to have them come on.

My options?

Have a chip burned to adjust the fan on/off temps.

or

Replace the 238* on switch mounted in the block/head with a switch that activates at around 185*-190*. This will cause the fan not controlled by my ECM to come on at the desired temp and the ECM fan to be the backup fan. If this can be done where is the switch and can I get a switch at any auto parts store?

I would burn a chip and be done with it, but this is a car I'm working on slowly and I'd hate to spend the money to burn a chip with the possibility of making changes that require a second chip burned.

On a side note, could I get a OBD1 computer from say a 94 or 95 Fbody and program it with the 89's program. I have the cable and software to flash these ECM's. This would eliminate the need for additional chip burns and I could tweak it myself. I doubt this is possible, if it were, I would have heard about it already. Is there any replacement computer for an IROC that can be flashed?

Thanks for the input!

 

Buy the fan switch. $35, Jet makes it, Jegs sells it. It is located in the middle of the pass. side head.
The OBD1 computer is 100% not compatible.

 

OK, I found the Jet switch at Jeg's. This is the right one, correct?

http://www.jegs.com/p/JET/752201/10002/-1

Now my question is, which fan is computer controlled? The one on the driver's side or passenger's side?

Can I run both fans off of this? There is another kit that looks like I could wire both fans to run off of this sensor, but it doesn't look as nice as the Jet kit.

http://www.jegs.com/p/Perma-Cool/744389/10002/-1

Also, other than cooling faster what would be the advantage of this. The Jet kit says it comes on at around 195 and goes out around 185. I don't want to over cool because the O2 is not heated and may not get hot enough to read correctly.

What is the coolest thermostat I can run and not have a situation where I'm borderlining open and closed loop. I'm looking at a 180*, but would that be too cold?

Thanks

 

That is the correct one. I would use the Perma-Cool one, however, so both fans work at the same time. I use a 170 deg. thermostat and have no o2 heating problems. Coolant temps have almost no effect on exhaust temps. Your ECM goes into closed loop at around 130 deg so its usually not effected by a cooler thermostat.